Strobe device for photography

ABSTRACT

A strobe device for photography, wherein there is provided a main discharge capacitor and light intensifying capacitor, that portion of the light resulting from the light emission of the main discharge capacitor which has been reflected by an object to be picked up is received by a photosensitive element, a silicon controlled rectifier is controlled by the output energy of the photoconductive element, and charges at the light-intensifying capacitor are discharged to a xenon discharge tube as occasion demands.

United States Patent lnventor Masaru Higuchi Osaka, Japan May 9, 1969 Dec. 7, 1971 West Electric Co., Ltd. Osaka, Japan May 15, 1968 Japan Appl. No. Filed Patented Assignee Priority STROBE DEVICE FOR PHOTOGRAPHY 10 Claims, 3 Drawing Figs.

US. Cl 315/241, 315/241 P, 315/151, 320/1 Int. Cl 1105b 37/00 Field 01 Search 315/241 P, 241, 151:320/1 References Cited UNITED STATES PATENTS 1/1946 Edgerton 2,624,831 1/1953 Farber 315/241 P 3,519,879 7/1970 Ogawa 315/241 X F OREIGN PATENTS 973,335 1/1960 Germany.... 315/241 P 1,051,404 2/1959 Germany 315/241 P OTHER REFERENCES Double Pulsing Boosts Flash Tube Performance," by J. H. Gonez and S. W. Park, Microwave, April, 1965.

Primary ExaminerJohn Kominski Assistant Examiner- Lawrence J Dahl Attorney-Stevens. Davis, Miller and Mosher ABSTRACT: A strobe device for photography, wherein there is provided a main discharge capacitor and light intensifying capaciton that portion of the light resulting from the light emission of the main discharge capacitor which has been reflected by an object to be picked up is received by a photosensitive element, a silicon controlled rectifier is controlled by the output energy of the photoconductive element, and charges at the light-intensifying capacitor are discharged to a xenon discharge tube as occasion demands.

PATENTE'B DEC 7 I97! 3, 525 2 5 L/GHT FL UX VOLTAGE INVENTOR rmsnnu Hlauun ATTORNEY S STROBE DEVICE FOR PHOTOGRAPHY This invention relates to a strobe device for photography, and more particularly it pertains to such devices of the automatic output light switching type wherein the output light is automatically switched in accordance with the distance therefrom to an object to be picked up and the reflection factorof the object.

ln an attempt to photographically pick up an object by the use of a strobe device for photography, it has heretofore been taken in conjunction with ''the accompanying drawings, in

which:

FIG. 1 is a circuit diagram showing the basic form of strobe device for photography according to an embodiment of the present invention;

FIG. 2 is a circuit diagram showing a concrete example of the device; and

FIG. 3 is a view illustrating variations with time in strobe light and voltages at various portions in the device.

The construction of. the present invention will now be described with reference to FIG. l,--the main portion of which is constituted by a circuit'comprising a xenon discharge tube 1 main discharge capacitor 9, trigger transformer 2, synchronized terminals 3 to be connected with the contact of a camera, resistors 4 and 4' for a trigger energy supplying circuit, trigger capacitor 5 and light intensifying capacitor 6, wherein a variable resistor and silicon controlled rectifier ll (referred to as SCR hereinafter) are connected in a'series loop with the circuit of the xenon discharge tube 1 and capacitor 9, and a photocell l2 and a capacitor l3for producing an integrating action are connected with the gate of the SCR 11.

FIG. 2 shows a circuit arrangement using a CdS or photoconductor or the like as the light receiving element wherein a voltage substantially identical with that occurring in the circuit constituted by the photocell l2 and capacitor 13 shown in FIG. 1 is obtained across a resistor 14. The circuit arrangement also includes a light receiving portion comprising resistors l6, l7, 19, 21 and 24, coupling'capacitors l5 and 20, transistors 18 and 22, and photoconductive element 23 formed by Cds or the like.

In operation, the xenon discharge tube 1 is made to emit light by closing the camera contact, as is well known in the art. Then, energy for the light emission is supplied by the capacitor 9. The light intensifying capacitor 6 is connected with a power source by terminals 7 and 8. Thus, by closing the synchroscope contacts 3, the charges, at the capacitor 9 are discharged to the xenon discharge tube 1' to start lightemission, and in the course of the discharge, a voltage difference occurs between the capacitor 9 and the" light increasing capacitor 6. This voltage difi'erence appears as a voltage drop across the variable resistor 10, and it 'is divided by the tap of the variable resistor and then applied as a positive bias voltage i of the gate of the SCR 1] through the resistor 14 to thereby render the SCR ll conductive. Thus, the energy stored in the light-intensifying capacitor 6 is permitted to flow into the xenon discharge tube 1. it is to be noted here that the output polarity of the photocell 12 is made opposite to that of this voltage. Therefore, when light is projected onto the photocell 12, a reverse voltage is produced which iscancelled out with the aforementioned positive bias voltage so that no voltage is imparted to the gate of the SCR 11 so that the latter is not rendered conductive. Hence, the xenon discharge tube 1 is made to emit light only by the energy stored in the capacitor 9. The capacitor 13 is provided for the purpose of integrating the output of the photocell 12 which is available when the light of the xenon tube which varies as indicated at A in FIG. 3 is projected onto the photocell after having been reflected by the object to be photographedi'ln FIG. 3, C indicates the case where the distance between the device and the object is so short that a large quantity of light is reflected by the object, D shows the case where the distance between the device and the object is so long that only a small quantity of light is reflected by'the object, and B indicates the voltage occurring at the midpoint of the variable resistor-l0. The SCR ll is'rendered conductive at a time during the ignition of the xenon discharge tube 1. On the assumption that the SCR is turned on at a point a in FIG. 3, for example, then the positive bias voltage applied to the gate of the SCR 11 is represented by is. However, by designing-the circuit so that the SCR is rendered conductive by a voltage difference as represented by T6, the SCR is turned on even in the case of D where the reflected lightinput is small; because in that case thereoccurs sucha voltage difference-as represented by H whichis greater than 2?. Thus,

the changednv capacitor 6 is discharged through the xenon discharge tube l so that shortage of the'light quantity at the 'object can be automatically compensated. in the case of C where the reflected light input is great, there occurs a voltage difference as represented by 55 which is smaller than 76 so that the SCR ll is not turned on so as to prevent the light-intensifying capacitor6 from being discharged. By selecting the bias voltage for the SCR by adjusting the variable resistor 10 as described above, the quantity of light canbe automatically controlled in accordance with the intensity of reflected light. Furthermore, the'device is adapted to be operated only by the light emanating from'the'xenon discharge tube '1 which has beenrefiected by the object'to be picked up and not by any other stroboscopic light. Thus, it is possible to prevent operational errors.

What is claimed is:

l. A strobe device for photography; comprising, a pair of power supply terminals; a first capacitor connected across said 7 pair of terminals; a series circuit of a xenon dischargetube and a silicon control rectifier connected across said pair of terminals; a trigger. circuit connected to said xenon discharge tube; aseries circuit of a second capacitor and a resistor connected across said pair of terminals; and means controlling the discharge'of said first capacitor in response to the quantity of light received by a photosensitive element to an intermediate tap on said resistor and to the control gate of said rectifier, wherein said photosensitive element has a reverse polarity with respect to the voltage on said tap, to thereby control current flow through said silicon control rectifier.

2. A strobe-device according to claim I, further comprising means imparting a voltage difference between said second capacitorand said first capacitor subsequent'to thelight emission by said'second capacitor through said tube, including a further resistor connected between said control gate and said tap.

3. A strobe device according to claim 1, wherein said resistor is a variable resistor'and saidtap is anadjustable tap.

4. A strobe device according to claim 1, further comprising meansintegrating the output of said photosensitive element, including a capacitor connected to the output of said photosensitive element.

5. Astrobe device according to claim 1, further comprising amplifying means operatively connected between the output of said photosensitive element and said control gate.

6. A strobe device for photography, comprising: a) a pair of power supply terminals b) a first series circuit of a xenon discharge tube having a trigger electrode and a silicon control rectifier having a gate electrode; c) a second series circuit of a I first light emitting capacitor and a variable resistance means to a junction point of said xenon' discharge tube and said silicon control rectifier; g) means generating a voltage responsive to light discharged from said discharge tube and reflected from an object illuminated by said discharge light, said voltage generating means being connected between said gate electrode and said movable tap such that said voltage is superimposed on a voltage drop across said resistance means and in the opposite polarity therewith to thereby control current flow through said rectifier; h) and switch means connected between said trigger electrode and said power supply terminals for controlling triggering of said trigger electrode.

7. A strobe device for photography as defined in claim 6, wherein said voltage generating means comprises a parallel circuit of a photo cell and a resistor.

8. A strobe device for photography as defined in claim 7 further comprising a third capacitor connected between said gate electrode and a cathode of said silicon control rectifier.

9. A strobe device for photography as defined in claim 6, wherein said voltage generating means comprises a transistor and photoconductive means connected to said transistor for generating a voltage at one electrode of said transistor in response to a variation in resistance in said photoconductive means.

10. A strobe device as defined in claim 9, further comprising a third capacitor connected between said gate electrode and a cathode of said silicon control rectifier.

l l t i 

1. A strobe device for photography, comprising, a pair of power supply terminals; a first capacitor connected across said pair of terminals; a series circuit of a xenon discharge tube and a silicon control rectifier connected across said pair of terminals; a trigger circuit connected to said xenon discharge tube; a series circuit of a second capacitor and a resistor connected across said pair of terminals; and means controlling the discharge of said first capacitor in response to the quantIty of light received by a photosensitive elements, including means connecting said photosensitive element to an intermediate tap on said resistor and to the control gate of said rectifier, wherein said photosensitive element has a reverse polarity with respect to the voltage on said tap, to thereby control current flow through said silicon control rectifier.
 2. A strobe device according to claim 1, further comprising means imparting a voltage difference between said second capacitor and said first capacitor subsequent to the light emission by said second capacitor through said tube, including a further resistor connected between said control gate and said tap.
 3. A strobe device according to claim 1, wherein said resistor is a variable resistor and said tap is an adjustable tap.
 4. A strobe device according to claim 1, further comprising means integrating the output of said photosensitive element, including a capacitor connected to the output of said photosensitive element.
 5. A strobe device according to claim 1, further comprising amplifying means operatively connected between the output of said photosensitive element and said control gate.
 6. A strobe device for photography, comprising: a) a pair of power supply terminals; b) a first series circuit of a xenon discharge tube having a trigger electrode and a silicon control rectifier having a gate electrode; c) a second series circuit of a first light emitting capacitor and a variable resistance means having an adjustable intermediate tap; d) a second capacitor for intensifying light emission from said first capacitor; e) means connecting said first series circuit, said second series circuit and said second capacitor, respectively, in parallel between said pair of power supply terminals; f) means connecting a junction point of said first capacitor and said resistance means to a junction point of said xenon discharge tube and said silicon control rectifier; g) means generating a voltage responsive to light discharged from said discharge tube and reflected from an object illuminated by said discharge light, said voltage generating means being connected between said gate electrode and said movable tap such that said voltage is superimposed on a voltage drop across said resistance means and in the opposite polarity therewith to thereby control current flow through said rectifier; h) and switch means connected between said trigger electrode and said power supply terminals for controlling triggering of said trigger electrode.
 7. A strobe device for photography as defined in claim 6, wherein said voltage generating means comprises a parallel circuit of a photo cell and a resistor.
 8. A strobe device for photography as defined in claim 7 further comprising a third capacitor connected between said gate electrode and a cathode of said silicon control rectifier.
 9. A strobe device for photography as defined in claim 6, wherein said voltage generating means comprises a transistor and photoconductive means connected to said transistor for generating a voltage at one electrode of said transistor in response to a variation in resistance in said photoconductive means.
 10. A strobe device as defined in claim 9, further comprising a third capacitor connected between said gate electrode and a cathode of said silicon control rectifier. 